JP2004079458A - Spark plug for multipoint ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug capable of stably burning even an extremely thin uniform air-fuel mixture. <P>SOLUTION: This spark plug 50 is equipped with an insulator part 51; a plurality of ignition gaps 81 exposed to the combustion chamber side of an engine from the surface of the insulator part 51; a conductive member 72 embedded in the insulator part 51 and connecting each ignition gap 81 to another ignition gap 81; and a terminal part 52 for applying a voltage to one of the ignition gaps 81. A capacitor X is formed between a cylinder head 2 of the engine and a part of the conductive member 72 embedded in the insulator part 51. When a predetermined high voltage is applied to the terminal part 52, sparks fly in the ignition gap 81 connected to the terminal part 52, and thereafter a chain of sparks fly in the adjacent ignition gaps 81. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a spark plug for a spark ignition engine.
[0002]
[Prior art]
In a spark ignition engine, as disclosed in JP-A-2001-123865, a spark plug is attached from above a combustion chamber, and a gap between a center electrode and an earth electrode is exposed at the center of the combustion chamber. When a predetermined high voltage is applied to the center electrode, sparks fly from the center electrode toward the ground electrode, and the mixture in the combustion chamber is ignited.
[0003]
[Problems to be solved by the invention]
However, in the above conventional spark plug, even if the spark plug has a plurality of side electrodes, only one spark is formed per spark plug, and only one ignition point exists in the combustion chamber. . Therefore, there is a problem that it is difficult to stably burn the air-fuel mixture when using an extremely thin air-fuel mixture in which fuel and air are almost uniformly mixed or when performing a large amount of exhaust gas recirculation (EGR). there were. This is because even if the air-fuel mixture is ignited reliably at the ignition point, the flame may be extinguished in the middle of propagation in an extremely thin air-fuel mixture with a slow flame propagation speed or an air-fuel mixture containing a large amount of EGR gas. This is because it becomes difficult for the flame to spread from the air-fuel mixture near the point. Further, there is an example in which two spark plugs are provided for each cylinder, but there are restrictions on the mounting location, and all are limited to two-valve engines.
[0004]
In this regard, there is a method in which the flame is agitated by using a gas flow such as squish, tumble flow, swirl, etc. to promote the combustion of the air-fuel mixture. However, in this method, another problem arises in that heat transfer to the combustion chamber wall surface is increased by gas flow, and heat loss increases.
[0005]
There is also a method in which a rich portion and a thin portion are formed in layers in the air-fuel mixture in the combustion chamber, and the rich air-fuel mixture is ignited so that the thin air-fuel mixture is burned, thereby burning an extremely thin air-fuel mixture as a whole ( Stratified combustion). However, in this method, when a rich air-fuel mixture burns, soot, unburned hydrocarbons (HC), and carbon monoxide (CO) are generated, and most of these are directly discharged into exhaust gas. In addition, there is a problem that nitrogen oxide (NOx) is easily generated when a thin portion is burned.
[0006]
The present invention has been made in view of the technical problems of the related art, and has as its object to provide an ignition plug that enables stable combustion to be performed even with an extremely thin uniform mixture.
[0007]
[Means for solving the problem]
According to a first aspect of the present invention, in the spark plug, an insulator portion, a plurality of ignition gaps exposed from a surface of the insulator portion toward a combustion chamber side of an engine, and a gap between the ignition gap embedded in the insulator portion. A conductive member to be connected, and a terminal portion for applying a voltage to one of the ignition gaps, wherein a capacitor is provided between a cylinder head of the engine and a portion of the conductive member embedded in the insulator portion. It is characterized by being formed.
[0008]
A second invention is characterized in that the plurality of ignition gaps in the first invention are connected in series by the conductive member.
[0009]
According to a third aspect of the present invention, in the spark plug, an insulator portion, a plurality of ignition gaps exposed from a surface of the insulator portion to the combustion chamber side of the engine, and a first conductive member connecting between the ignition gap and the ignition gap. A first conductive member, a second conductive member disposed at a gap from the first conductive member, and a terminal portion for applying a voltage to one of the ignition gaps; A capacitor is formed between the member and the second conductive member.
[0010]
A fourth invention is characterized in that the plurality of ignition gaps in the third invention are connected in series by the first conductive member.
[0011]
A fifth invention is characterized in that the first conductive member according to the third or fourth invention is embedded in the insulator portion.
[0012]
A sixth invention is characterized in that the second conductive member according to the third to fifth inventions is embedded in the insulator portion.
[0013]
A seventh invention is characterized in that the second conductive member according to the third to fifth inventions covers a portion other than the combustion chamber side surface of the insulator portion.
[0014]
An eighth invention is characterized in that in the first to seventh inventions, the insulator portion is a rod-shaped member, and the plurality of ignition gaps are provided along the axial direction of the insulator portion. .
[0015]
A ninth invention is characterized in that, in the eighth invention, when the spark plug is attached to the engine, a tip portion of the insulator contacts a cylinder head of the engine to ground the spark plug. It is.
[0016]
A tenth invention is characterized in that the distal end of the insulator portion according to the eighth or ninth invention is held by sliding fit in a recess formed in a cylinder head of the engine.
[0017]
An eleventh invention is an engine according to the eighth to tenth inventions, wherein the engine has two intake ports and two exhaust ports, and the ignition plug is provided between two intake port valve seats and two exhaust ports. The spark plug according to any one of claims 8 to 10, wherein the spark plug is attached to the engine so as to pass between a valve seat of an exhaust port.
[0018]
According to a twelfth aspect, in the eighth to eleventh aspects, the cross section of the insulator portion has a shape in which the cylinder axis direction is longer than the cylinder axis direction of the engine and the direction perpendicular to the axis direction of the insulator portion. It is characterized by the following.
[0019]
According to a thirteenth aspect, in the first to twelfth aspects, a positioning means for opening the ignition gap to a combustion chamber side of the engine is further provided.
[0020]
A fourteenth invention is characterized in that the positioning means in the thirteenth invention is a spline fitting for restricting relative rotation of the spark plug with respect to the cylinder head.
[0021]
In a fifteenth aspect based on the first to fourteenth aspects, a groove is formed in a surface of the cylinder head of the engine on the side of the combustion chamber, and a side of the spark plug opposite to the combustion chamber is formed in a groove of the cylinder head. It is attached to the engine so as to be buried.
[0022]
In a sixteenth aspect based on the first to fifteenth aspects, the spark plug is inserted into a cylinder head of the engine from an intake port side surface of a cylinder head of the engine, whereby the spark plug is attached to the engine. It is characterized by the following.
[0023]
According to a seventeenth aspect, a multi-point ignition engine is provided with the spark plug according to the first to sixteenth aspects, and is operated at a lean air-fuel ratio.
[0024]
[Action and effect]
In the spark plug according to the present invention, when a predetermined high voltage is applied to the terminal, first, discharge occurs in the ignition gap connected to the terminal. The high voltage is also transmitted to the adjacent ignition gap through the conductive member, so that discharge occurs in the adjacent ignition gap. By repeating this, discharge occurs in a plurality of ignition gaps in a chain at substantially the same time, and stable combustion can be performed even with an extremely thin uniform mixture.
[0025]
Such multipoint simultaneous ignition becomes possible because a minute capacitor is formed between the conductive member that connects the ignition gap and the cylinder head of the engine, and the electric charge stored there is sparked. This is because it contributes to generation. That is, when a discharge occurs in a certain ignition gap, an excess of the electric charge occurs in a capacitor between the ignition gap and an adjacent ignition gap, thereby applying a high voltage to the adjacent ignition gap and causing a discharge. is there. In particular, by embedding the conductive member in the insulator portion of the spark plug, the distance between the conductive member and the cylinder head is shortened to form a capacitor having a sufficient capacity, thereby enabling stable spark generation (first example). , The second invention).
[0026]
Such a capacitor contributing to spark generation can be formed between a conductive member (first conductive member) that connects between two adjacent ignition gaps and the cylinder head, and also has a first conductive property. The second conductive member may be arranged with a gap between the members and formed between the first conductive member and the second conductive member (third and fourth inventions). According to this configuration, since the capacitance of the capacitor is determined by the distance between the first conductive member and the second conductive member, it is not necessary to embed the first conductive member in the insulator of the ignition plug. A capacitor having a capacity can be formed, and the capacitance of the capacitor can be optimized by adjusting the distance between the first conductive member and the second conductive member.
[0027]
Also in such a configuration, the first conductive member is embedded in the insulator portion (fifth invention), and the second conductive member is also embedded in the insulator portion (sixth invention). For example, the first conductive member and the second conductive member are closer to each other, so that a capacitor having a larger capacity can be formed.
[0028]
Further, if the second conductive member is configured to cover a portion other than the surface of the insulator portion on the side of the combustion chamber, the strength of the insulator portion is supplemented, and the escape of heat from the insulator portion to the cylinder head is promoted. Yes (seventh invention). Further, by changing the area and position of the second conductive member covering the insulator portion, and the material and thickness of the second conductive member, the heat value of the ignition plug can be adjusted.
[0029]
The spark plug for multipoint ignition can be configured, for example, by providing the insulator portion as a rod-shaped member and providing a plurality of ignition gaps in the axial direction of the insulator portion (eighth invention). In this configuration, it is preferable to apply the output voltage to the ignition gap closest to the terminal first, and to cause discharge in order from the ignition gap closest to the terminal, but to apply the voltage to the center of the insulator part. And the discharge may occur from the center of the insulator to the end of the insulator, or a voltage may be applied to the tip of the insulator to cause the discharge to occur sequentially toward the terminal. Is also possible.
[0030]
Further, if the spark plug is grounded by bringing the tip of the insulator into contact with the cylinder head, the configuration of the spark plug can be simplified (a ninth invention). Is held in the recess formed in the cylinder head by sliding fit, thermal expansion of the spark plug and the cylinder head can be absorbed (tenth aspect).
[0031]
Further, when applied to a four-valve engine, if the spark plug is mounted so as to pass between the valve seats of the two intake ports and between the valve seats of the two exhaust ports, interference between the valves and the spark plug is avoided. And the ignition gap can be arranged in the combustion chamber so as to cross the combustion chamber (eleventh invention). At this time, if the cross section of the insulator portion is configured to have a shape in which the cylinder axis direction is longer than the cylinder axis direction and the direction perpendicular to the axis direction of the insulator portion, for example, an oval shape or an elliptical shape that is longer in the cylinder axis direction, the The spark plug can be easily attached while securing the strength of the plug (twelfth invention).
[0032]
Further, since the spark plug needs to be attached to the cylinder head so that the ignition gap is correctly directed to the combustion chamber side, it is preferable to provide a positioning means for the spark plug (the thirteenth invention). Such a positioning means may be, for example, a spline fitting for restricting the relative rotation of the spark plug with respect to the cylinder block (a fourteenth invention).
[0033]
In addition, although the spark plug is exposed to the combustion chamber and receives high temperatures associated with combustion, if a groove is formed on the surface of the cylinder head on the side of the combustion chamber and a part of the spark plug is embedded in the groove, ignition can be performed. The amount of heat received by the plug can be reduced, and heat loss of the ignition plug can be prevented (the fifteenth invention). Further, if the ignition plug is mounted from the intake port side of the cylinder head, the terminal of the ignition plug, the high-pressure cord connected thereto, and the like are arranged on the intake port side where the temperature is lower than the exhaust port side. Can be protected from high heat (a sixteenth invention).
[0034]
By applying the above spark plug to a spark ignition engine, stable ignition and combustion can be performed even with an air-fuel ratio of about 30 which is super-lean and air-fuel ratio, thereby greatly improving the fuel efficiency and exhaust performance of the engine. (17th invention).
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0036]
1 and 2 show a schematic configuration of a spark ignition engine 1 to which a spark plug according to the present invention is applied. FIG. 1 is a longitudinal sectional view of the engine 1, and FIG. It is the figure seen from the room side.
[0037]
The engine 1 is a four-valve engine having two intake valves and two exhaust valves. The cylinder head 2 is attached to the cylinder block 3 via a gasket (not shown), and a combustion chamber 4 is formed between the cylinder head 2 and the cylinder block 3. The combustion chamber 4 is a so-called pent roof type combustion chamber, and includes a cylindrical portion connected to the cylinder of the cylinder block 3, an intake side slope and an exhaust side slope connected to the upper end of the cylinder portion, and a crown surface of the piston 5.
[0038]
The intake ports 8a and 8b are opened on the intake side slope, and a mixture of fuel and air mixed in advance so as to be uniform is introduced into the combustion chamber 4 from here. After the air-fuel mixture introduced into the combustion chamber 4 is compressed by the piston 5, it is ignited by a spark generated by the gaps 81 of the spark plug 50. The combustion gas pushes down the piston 5, and is discharged from the exhaust ports 9a and 9b opened on the exhaust side slope to the exhaust passage (not shown) by the piston 5 rising again.
[0039]
The ignition plug 50 is inserted into the groove 33 formed in the combustion chamber 4 side surface of the cylinder head 2 so that a part of the upper part is buried in the cylinder head 2 and is parallel to the bottom surface of the cylinder head 2. A plurality of ignition gaps 81 facing the combustion chamber 4 side (downward in the cylinder axial direction) are provided at equal intervals in the insulator portion 51 of the ignition plug 50 so as to cross the combustion chamber 4. . Part of the spark plug 50 is buried in the cylinder head 2 in order to reduce the amount of heat received from the combustion gas in the combustion chamber 4 by the spark plug 50 and prevent heat loss of the spark plug 50.
[0040]
A terminal 52 of the ignition plug 50 protrudes from a side surface of the cylinder head 2 on the side of the intake port, and a high voltage cord for supplying a predetermined high voltage from an external battery and an ignition coil is connected to the terminal 52 (not shown). ). Although the ignition plug 50 has six ignition gaps 81 in this embodiment, seven or more ignition gaps or less than six ignition gaps may be provided.
[0041]
The spark plug 50 is attached to the cylinder head 2 so as to pass through the center of the combustion chamber 4, that is, a portion where the height of the combustion chamber 4 in the cylinder axis direction (longitudinal direction) is highest, and cross the combustion chamber 4. In this embodiment, as shown in FIG. 2, the ignition plug 50 passes between the valve seats 8c and 8d of the intake ports 8a and 8b and between the valve seats 9c and 9d of the exhaust ports 9a and 9b. When viewed from the side, the combustion chamber 4 is mounted so as to be equally divided by the spark plug 50.
[0042]
A circular stepped spark plug mounting hole 31 is formed in the side surface of the cylinder head 2 on the intake port side. By making the mounting hole 31 stepped, the large-diameter portion 61 of the ignition plug 50 comes into contact with the step 32 inside the mounting hole 31 when the ignition plug 50 is mounted, and the ignition plug 50 is positioned in the axial direction. can do.
[0043]
In order to mount the spark plug 50 to the cylinder head 2, first, the spark plug 50 is inserted into the mounting hole 31, and the tip end 50 e of the spark plug 50 is inserted into the cylindrical recess 32 formed on the exhaust port side of the combustion chamber 4. It is slidably held in a sliding direction. When the spark plug 50 is attached from the intake port side of the cylinder head 2, the terminal 52 and the high pressure cord are located on the intake port side if attached from the intake port side, and these are protected from high heat on the exhaust port side. Because you can do it.
[0044]
Then, a concave ridge 42 of the flange member 41 as shown in FIG. 3 is spline-fitted to a convex ridge 64 (see FIG. 6) formed on the side surface of the large diameter portion 61 of the spark plug 50 and extending in the axial direction of the spark plug 50. Then, a bolt (not shown) is passed through the mounting hole 43 of the flange member 41 and fixed to the side surface of the cylinder head 2 on the intake port side. By adopting such a mounting structure, the ignition plug 50 can be mounted on the cylinder head 2 so that the ignition gap 81 faces the combustion chamber 4 accurately.
[0045]
FIG. 4 is a cross-sectional view of the cylinder head 2 and shows a cross section taken along line AA of FIG. The ignition plug 50 is attached to the combustion chamber 4 so as to pass between the valve seats 8c and 8d of the intake ports 8a and 8b of the cylinder head 2. On the upper surface of the combustion chamber 4, that is, on the intake side slope and the exhaust side slope, a concave groove 33 for receiving a part of the ignition plug 50 is formed parallel to the bottom surface of the cylinder head 2.
[0046]
FIG. 5 is also a cross-sectional view of the cylinder head 2 as in FIG. The concave groove 33 for mounting the spark plug is formed slightly longer than the insulator portion 51, so that a margin is provided at the tip of the tip of the spark plug 50 when the spark plug 50 is mounted. With this allowance, thermal expansion of the spark plug 50 and the cylinder head 2 during engine operation can be absorbed, and damage to the spark plug 50 can be prevented.
[0047]
FIG. 6 is a diagram showing a detailed structure of the ignition plug 50. The ignition plug 50 includes a rod-shaped insulator portion 51 made of an insulating material, a terminal 52 connected to an end portion of the insulator portion 51, a grounding metal fitting 53 connected to a tip portion 51 e of the insulator portion 51, and a terminal side of the insulator portion 51. It comprises a base metal fitting 54 mounted on the outer periphery for mounting the spark plug 50 to the cylinder head 2 of the engine 1.
[0048]
The base fitting 54 includes a large-diameter portion 61 and a small-diameter portion 62. The large-diameter portion 61 is a portion corresponding to the hexagonal portion of the conventional spark plug, but does not have a nut portion for tightening unlike the conventional spark plug, and instead has a larger diameter than the large-diameter portion 61. A large flange 63 is provided. In addition, on the outer peripheral surface of the large-diameter portion 61, there is provided a ridge portion 64 extending from the flange portion 63 in the axial direction of the spark plug 50, and is used as a positioning member when the spark plug 50 is attached to the cylinder head 2. . The conventional mounting method in which a hexagonal portion and a screw portion are provided and a screw is screwed into a cylinder head unlike a conventional spark plug is not adopted. In the screwing method, the ignition gaps 81a to 81f are accurately directed toward the combustion chamber 4. Is difficult.
[0049]
First to sixth ignition gaps 81a to 81f are linearly and equidistantly provided in a portion of the insulator portion 51 exposed in the combustion chamber 4, and a spark plug 50 is provided at a leading end portion 51e of the insulator portion 51. Is attached to the cylinder head 2. The grounding member 53 functions to contact the cylinder head 2 with the spark plug 50 attached to the cylinder head, and to release the voltage applied to the spark plug 50 to the cylinder head 2.
[0050]
FIG. 7 shows a longitudinal section of the ignition plug 50. When a predetermined high voltage is applied to the terminal 52, the high voltage is applied to the terminal-side electrode of the first ignition gap 81a via the resistor 65, and discharge occurs from the terminal-side electrode to the ground-side electrode. As a result, a high voltage is also applied to the terminal-side electrode of the second ignition gap 81b, and a discharge also occurs in the second ignition gap 81b. Thereafter, even after the third ignition gap 81c, discharge occurs continuously in a chain, and multipoint simultaneous ignition of the air-fuel mixture is realized.
[0051]
Here, the first to sixth ignition gaps 81 a to 81 f are connected to the terminal 52, pass through the inside of the base fitting 54, and have an end 71 a exposed to the combustion chamber 4 from the lower surface of the insulator 51. The terminal-side electrode member 71 and the first to fifth intermediate electrode members 72 in which the electrode portions 72a and 72b are exposed from the surface of the insulator portion 51 toward the combustion chamber 4 and the connecting portion 72c is embedded in the insulator portion 51. And an L-shaped earth-side electrode member 73 connected to the earthing metal fitting 53 and having an end 73 a exposed from the surface of the insulator 51 toward the combustion chamber 4. No three or more ignition gaps are connected to one intermediate electrode member 72, and the ignition gaps 81a to 81f are connected in series by the intermediate electrode member 72. Each of the electrode members 71 to 73 is formed of a conductive member having a small electric resistance.
[0052]
As shown in FIG. 8, the intermediate electrode member 72 includes electrode portions 72a and 72b forming a terminal-side electrode and an earth-side electrode, and a connecting portion 72c connecting the two electrode portions 72a and 72b. Is fixed to the insulator portion 51 by being embedded in the insulator portion 51. By embedding the connecting portion 72c in the insulator portion 51, the intermediate electrode member 72 can be firmly fixed to the insulator portion 51. In addition, the distance between the connecting portion 72c and the cylinder head 2 is shortened, and the connecting portion 72c and the cylinder head 7, a capacitor having a sufficient capacity (shaded area X in FIG. 7) can be formed.
[0053]
Furthermore, in order to suppress the voltage drop in the connecting portion 72c and generate the same spark in each of the ignition gaps 81a to 81f, the resistance of the connecting portion 72c is set to be negligibly small. Here, since the connecting portion 72c is straight, the shape of the intermediate electrode member 72 is U-shaped, but both electrode portions 72a and 72b are exposed in the combustion chamber 4 and the connecting portion 72c is embedded in the insulator portion 51. It may have another shape such as a U-shape as long as the two electrode portions 72a and 72b are connected.
[0054]
The ends 71a, 72a, 72b, 73a of the electrode members 71-73 exposed from the insulator portion 51 toward the combustion chamber 4 have a needle-like shape that becomes thinner as approaching the tip so that sparks can fly easily. Constitute ignition gaps 81a-81f. A heat-resistant metal, for example, platinum, iridium, or the like is used for each part constituting the ignition gaps 81a to 81f.
[0055]
Further, if the height of the exposed portions of the ends 71a, 72a, 72b, 73a of the electrode members 71-73 from the surface of the insulator portion is increased, the mixture can be easily ignited, but the exposed heights thereof are too large. When the spark plug 50 is mounted on the cylinder head 2, the ends of the electrode members 71-73 interfere with the spark plug mounting hole 31, specifically, the step on which the small diameter portion 62 is seated. Therefore, the end portions of the electrode members 71-73 are set so that the maximum radius of the insulator portion 51 including the electrode portion is smaller than the minimum radius of the cross section of the base metal fitting 54, that is, the radius of the cross section of the small diameter portion 62. The exposed height is set to be smaller than the difference between the radius of the insulator portion 51 and the radius of the small-diameter portion 62 of the base fitting 54.
[0056]
In order to seal the high-pressure gas in the combustion chamber 4 from the outside, a sealing material 75 is sealed between the insulator 51 and the base metal fitting 54 as in the conventional ignition plug. Gaskets 76 and 77 are sandwiched between the base metal fitting 54 and the base fitting 54.
[0057]
Next, the features of the spark plug having the above structure and the operation and effects of the engine including the spark plug having the above structure will be described. In the ignition plug 50 having the above configuration, when a predetermined high voltage is applied to the terminal 52, discharge occurs sequentially from the ignition gap 81 a near the terminal 52, and is finally grounded by the grounding metal fitting 53 and the cylinder head 2. In other words, when a spark flies in a certain ignition gap, a high voltage is also applied to an ignition gap adjacent to the spark, and sparks are generated one after another in a chain. Here, since the speed at which the current flows is almost infinite, the discharge in each ignition gap occurs almost simultaneously. Such simultaneous ignition is enabled only by a minute capacitor between the cylinder head 2 and the connecting portion 72c (conductor such as nickel) connecting the ignition gaps 81a-81f, as indicated by the hatched portion X in FIG. Is formed, and the electricity stored in the minute capacitor also contributes to spark generation.
[0058]
In the spark plug according to the present invention, in particular, since ignition is performed at multiple points, the initial combustion ratio of the air-fuel mixture increases in proportion to the number of ignition gaps as compared with the case of a single conventional spark plug. As a result, it has been conventionally said that the air-fuel ratio is about 20 (the theoretical air-fuel ratio is 14.7) as the limit of combustion, but the engine is stable even at an ultra-lean air-fuel ratio of 30 which is much thinner than that. It becomes possible to drive. Further, since the air-fuel mixture is easily ignited, the cold startability is also improved.
[0059]
In addition, the energy of the high voltage to be supplied is not proportional to the number of ignition gaps, although the number of ignition gaps is large, and it is sufficient that the energy is about twice that in the case of conventional single-point ignition. This is because the minute capacitor contributes to spark generation, and even though spark generation in each ignition gap is performed almost simultaneously, there is a very microscopic time delay for each ignition gap. It is considered that sparks are not simultaneously generated in the ignition gap.
[0060]
FIG. 9 shows the results of a comparison experiment of the burned ratio with respect to the crank angle of six-point ignition and two-point ignition in an engine provided with the spark plug according to the present invention.
[0061]
In this comparative experiment, the air-fuel ratio was approximately 30 (accurately 29.9) and uniform, the rotation speed was constant (900 rpm), and the ignition timing was 15 degrees before the top dead center. It can be seen that almost 30 degrees after the completion of the combustion, and rapid combustion of 15% / degree or more is performed.
[0062]
As described above, according to the present invention, rapid combustion can be realized by multipoint simultaneous ignition, so that super-lean burn with a uniform air-fuel mixture having an air-fuel ratio of about 30 and a large amount of exhaust gas recirculation become possible. In particular, ultra lean burn significantly improves fuel economy and reduces emissions in exhaust gases to levels that require little catalyst. Further, even when a catalyst is used to further reduce exhaust emissions, the amount of emissions to be treated by the catalyst is reduced, so that the amount of catalyst can be reduced.
[0063]
Subsequently, a second embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a configuration diagram of an ignition plug 50 according to the second embodiment, FIG. 11 is a vertical cross-sectional view thereof, and FIG. 12 is a CC cross-sectional view of FIG. The same components as those in the first embodiment are denoted by the same reference numerals.
[0064]
In the first embodiment, the insulator portion 51 of the ignition plug 50 has a substantially circular cross section. In the second embodiment, however, as shown in FIGS. h (width in the cylinder axis direction) is smaller than h (width in the cylinder axis direction and the direction perpendicular to the axis direction of the ignition plug), here an elliptical shape, and the ignition plug 50 is mounted in the middle of the valve seat. In addition to reducing the width w, the strength reduction due to the reduced width w is reduced.
[0065]
In addition, a protective fitting 55 (second conductive member) that protects the insulator portion 51 and also serves as a ground from the ground side electrode member 73 to the spark plug mounting portion is mounted on the outer periphery of the insulator portion 51. The protection fitting 55 is fixed to the insulator 51 by, for example, welding. The protection bracket 55 is attached so as to embrace most of the insulator portion 51 except for the surface on the combustion chamber 4 side, supplements the mechanical strength of the insulator portion 51, and promotes escape of heat from the insulator portion 51 to the cylinder head 2. I do. If the material and thickness of the protective fitting 55 or the position and area of the protective fitting 55 covering the insulator 51 are adjusted, and the manner in which heat is transferred from the ignition plug 50 to the protective fitting 55 and the cylinder head 2 is adjusted, the insulator It is also possible to adjust the temperature of 51 and the heat value of the spark plug 50.
[0066]
Furthermore, in the previous embodiment, a capacitor was formed between the cylinder head 2 and the connecting portion 72c, and this contributed to continuous ignition. In this embodiment, however, a capacitor was provided between the protective fitting 55 and the connecting portion 72c. Formed, which will contribute to continuous ignition. Since the distance between the protective fitting 55 and the connecting portion 72c is shorter than the distance between the cylinder head 2 and the connecting portion 72c, a larger capacity capacitor can be formed, and strong and reliable multipoint continuous ignition is realized. can do.
[0067]
Here, the protection fitting 55 also serves as a ground to the ignition plug mounting portion, but the voltage applied to the ignition plug 50 is made to escape from the tip to the cylinder head 2 in the same manner as in the previous embodiment. May be used exclusively for protecting the spark plug and adjusting the heat value. In addition, the protection fitting 55 may be embedded in the insulator portion 51. In this case, the distance between the protection fitting 55 and the connecting portion 72c is shortened, and a capacitor having a larger capacity can be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an engine provided with a spark plug according to the present invention.
FIG. 2 is a view of a cylinder head of the engine as viewed from a combustion chamber side.
FIG. 3 is a diagram showing a spark plug mounting flange.
FIG. 4 is a cross-sectional view of the cylinder head (AA cross section in FIG. 2).
5 is a cross-sectional view of the cylinder head (a cross-section taken along line BB in FIG. 2).
FIG. 6 is a configuration diagram of a spark plug.
FIG. 7 is a longitudinal sectional view of a spark plug.
FIG. 8 is an enlarged view of an intermediate electrode member.
FIG. 9 is a characteristic diagram showing a relationship between a crank angle, a burned rate, and a heat release rate, and is a comparison between a case of two-point ignition and a case of six-point ignition.
FIG. 10 is a configuration diagram of a spark plug according to a second embodiment.
FIG. 11 is a longitudinal sectional view of a spark plug according to a second embodiment.
FIG. 12 is a cross-sectional view of the spark plug according to the second embodiment (a cross section taken along line CC in FIG. 11).
[Explanation of symbols]
2 Cylinder head
4 Combustion chamber
8a, 8b Intake port
9a, 9b Exhaust port
50 spark plug
51 Insulator part
52 Terminal
53 Grounding bracket
55 Protection bracket (second conductive member)
64 ridges
71-73 electrode member
72 connecting portion (conductive member, first conductive member)
81 (81a-81f) ignition gap
X capacitor

Claims (17)

Insulator part,
A plurality of ignition gaps exposed from the surface of the insulator portion to the combustion chamber side of the engine;
A conductive member embedded in the insulator portion and connecting between the ignition gap and the ignition gap;
A terminal section for applying a voltage to one of the ignition gaps,
Wherein a capacitor is formed between a cylinder head of the engine and a portion of the conductive member embedded in the insulator portion. The spark plug according to claim 1, wherein the plurality of ignition gaps are connected in series by the conductive member. Insulator part,
A plurality of ignition gaps exposed from the surface of the insulator portion to the combustion chamber side of the engine;
A first conductive member connecting between the ignition gap and the ignition gap;
A second conductive member disposed with a gap from the first conductive member;
A terminal section for applying a voltage to one of the ignition gaps,
And a capacitor is formed between the first conductive member and the second conductive member. The spark plug according to claim 3, wherein the plurality of ignition gaps are connected in series by the first conductive member. The spark plug according to claim 3, wherein the first conductive member is embedded in the insulator portion. The spark plug according to any one of claims 3 to 5, wherein the second conductive member is embedded in the insulator portion. The spark plug according to any one of claims 3 to 5, wherein the second conductive member covers a portion other than the surface of the insulator portion on the combustion chamber side. The spark plug according to any one of claims 1 to 7, wherein the insulator portion is a rod-shaped member, and the plurality of ignition gaps are provided side by side in the axial direction of the insulator portion. 9. The spark plug according to claim 8, wherein when the spark plug is attached to the engine, a tip end of the insulator contacts a cylinder head of the engine to ground the spark plug. The spark plug according to claim 8, wherein a tip end of the insulator portion is held in a recess formed in a cylinder head of the engine by sliding fit. The engine has two intake ports and two exhaust ports,
11. The engine according to claim 8, wherein the spark plug is attached to the engine so as to pass between valve seats of two intake ports and between valve seats of two exhaust ports. The spark plug as described. 12. The insulator according to claim 8, wherein a cross section of the insulator is longer in a cylinder axis direction than in a cylinder axis direction of the engine and a direction perpendicular to the axis direction of the insulator portion. The spark plug according to one of the above. 13. The spark plug according to claim 1, further comprising positioning means for opening the ignition gap to a side of the combustion chamber of the engine. 14. The spark plug according to claim 13, wherein the positioning means is a spline fitting for restricting a relative rotation of the spark plug with respect to the cylinder head. A groove is formed in the combustion chamber side surface of the cylinder head of the engine,
The spark plug according to any one of claims 1 to 14, wherein the spark plug is attached to the engine such that a side opposite to a combustion chamber is buried in a groove of the cylinder head. 16. The engine according to claim 1, wherein the spark plug is inserted into a cylinder head of the engine from a side of an intake port of the cylinder head of the engine, whereby the spark plug is attached to the engine. The spark plug according to 1. A multi-point ignition engine comprising the spark plug according to any one of claims 1 to 16 and operated at a lean air-fuel ratio.

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